Location: Crop Genetics and Breeding Research2012 Annual Report
1a. Objectives (from AD-416):
The long term objective for this project is the development of peanut germplasm with resistance to economically significant biotic and abiotic stresses. Over the next five years, we will focus on the following specific objectives: 1) Develop peanut germplasm with resistance to preharvest aflatoxin contamination; 2) Develop peanut germplasm with high oleic acid and resistance to the peanut root-knot nematode and tomato spotted wilt virus; 3) Develop peanut germplasm with improved drought resistance; and 4) Devise strategies to assess the genetic diversity for traits that will be important for the economical production of biodiesel from peanut.
1b. Approach (from AD-416):
Breeding populations will be developed by hybridizing high yielding cultivars with sources of resistance to preharvest aflatoxin contamination (1) and sources of resistance to drought (3). These populations will be evaluated under field conditions with drought and heat stress imposed by covering the entire test area with a mobile greenhouse. Aflatoxin contamination of the subsequent yield will be determined using the immunoaffinity column fluorometer method. Progeny will be selected based on relatively low aflatoxin contamination (1) and/or relatively high pod yields (3). 2) Breeding populations will be developed by hybridizing cultivars with high oleic acid with high yielding breeding lines with resistance to the peanut root-knot nematode and tomato spotted wilt virus. These populations will be tested for resistance to nematodes using a greenhouse screening technique. Progenies exhibiting nematode resistance will be field tested for virus resistance, and resulting selections will be analyzed for fatty acid composition. 4) A revised and updated core collection will be used to access genetic diversity for important characteristics for economical productions of biodiesel (pod yield, meat content, percent oil, and disease resistance).
3. Progress Report:
Sources of resistance to preharvest aflatoxin contamination (PAC) were hybridized with high yielding cultivars in a continuing effort to develop breeding populations for selection. Over 100 late generation breeding lines were grown under heat and drought stressed field conditions and evaluated for aflatoxin contamination. Several showed at least a 70% reduction in aflatoxin contamination compared to susceptible controls. Some of these lines also had high yield and good resistance to tomato spotted wilt virus (TSWV). Sources of resistance to nematodes were hybridized with high yielding breeding lines with resistance to TSWV in a continuing effort to develop breeding populations for selection. Over 1000 late generation breeding lines were tested for nematode resistance in greenhouse trials, and for TSWV resistance in field studies. We identified over 100 breeding lines having resistance to both pathogens. Marker assisted selection was utilized in a backcrossing program and in segregating populations to develop breeding lines with high oleic acid and resistance to nematodes and TSWV. Sources of resistance to drought were hybridized with high yielding cultivars in a continuing effort to develop breeding populations for selection. Over 50 late generation breeding lines were grown under drought stressed field conditions and evaluated for pod yield. Several showed high yield relative to susceptible controls. Some of these lines also had high yield and good resistance to TSWV and PAC.
1. Effect of Genotype on Tomato Spotted Wilt in Peanut. Tomato spotted wilt virus (TSWV) can cause devastating yield losses in peanut, particularly when susceptible varieties are grown at low plant densities. One objective of this study was to compare the effect of seeding rate and the resultant plant density within the row on spotted wilt in the moderately susceptible cultivar Georgia Green and four new advanced breeding lines. An equally important objective was to determine if field resistance in these lines is sufficient to allow use of reduced seeding rates compared to the standard rate of 6 seed per foot of row typically used for Georgia Green. All of the breeding lines had significantly higher resistance to TSWV in comparison to Georgia Green. The yields for these breeding lines at the lower seeding rate were higher than the yield of Georgia Green at the higher seeding rate. Farmers will be able to save costs and increase profitability by using lower seeding rates with these highly resistant lines.
2. Release of a Nematode Susceptible Sister Line of ‘Tifguard’. Experimental tools are needed to better understand the impact of nematodes on peanut production. TifGP-2 is a nematode-susceptible late generation derived sister line of Tifguard, a peanut variety that has high resistance to both the peanut root-knot nematode and tomato spotted wilt virus (TSWV). These highly related sister lines with and without nematode resistance can be valuable research tools to obtain a better understanding of the interactions of nematodes with other pathogens of peanut. These sister lines should also be valuable tools for research on resistance mechanisms and genetic control of nematode resistance in peanut.
Girdthai, T., Jogloy, S., Vorasoot, N., Akkasaeng, C., Wongkaew, S., Holbrook Jr, C.C., Patanothai, A. 2011. Heritability of, and genetoypic correlations between, aflatoxin traits and physiological traits for drought tolerance under end of season drought of peanut (Arachis hypogaea L.). Field Crops Research. 118:169-176.